Most embarrassing thing, you have ever done.. growing up?

Here's mine, from what I remember, one time I was in the gym with a friend of mine and there was another girl look my way and she kept talking and smiling and I wave back and I say "What? I can't hear you!" and she was like "I'm talking to the other girl, behind you.." and well, after that I sure as hell never replied to someone waving or talking to me from far, lol.